The investigator proposes to compare viral envelope and infectious viral constructs of HIV in which known enhancing domains have been genetically manipulated with the objective of minimizing enhancing capacity while retaining protective immune function. The generation of protective versus enhancing responses will be quantitated in rabbits and guinea pigs and by analysis of enhancing monoclonal antibodies binding to mutant constructs. In addition to the primary goal of producing HIV immunogens capable of inducing protective immune responses without the induction of enhancing antibodies, the analysis may provide basic data on the role of the conserved immunodominant domains of the viral envelope proteins. The author has five specific aims, the first of which is to evaluate systematic mutations within the primary immunodominant domains of gp120 and gp41 with respect to stability and level of expression of mutant env products as compared to controls, using the HIV env expression vector pDOLHIVenv. Secondly, the investigator proposes to evaluate the immunological properties of stable mutant gp120 and gp41 proteins by examining their capacity to generate neutralizing antibodies in rabbits and guinea pigs and their quantitative capacity to bind human enhancing monoclonal antibodies. Next, he will try to determine systematically the relative role which specific amino acids in the primary immunodominant domains of gp120 and gp41 play in the induction of enhancing antibodies and in the retention of viral infectivity. Fourth, the author will attempt to evaluate the biological activity of infectious recombinant clones by an examination of the range of cell targets, the infectious viral yields, cytopathicity and the ability to form syncytia in vitro. Lastly, the investigator proposes to evaluate the immunological properties of infectious recombinant HIV mutants by an examination of their capacity to generate neutralizing antibodies in rabbits and guinea pigs, PBMC (peripheral blood mononuclear cells) proliferative responses and the ability of human polyclonal and human monoclonal enhancing antibodies to enhance their infectivity in enhancing assays.